While proceeding up the deeper portion of the Amherstburg Channel, the forward speed of the VULCAN was observed to have decreased. The reduction in speed was due to a fall in the number of RPM of the main engine. Because the engine-room staff had not informed the bridge that a change-over from heavy to diesel fuel was taking place, which change-over normally requires a reduction in RPM, those on the bridge were not immediately aware of the cause of the loss of speed. The GPS speed reading of 5.5 to 5.6 knots was briefly taken as an indication by the pilot that the current in the area was abnormally strong. Because he suspected that the current was abnormally strong, the pilot intended to direct the vessel towards the western side of the channel to make allowance for the set he anticipated would set the vessel bodily to starboard after passing light 'D71'. Although the pilot discussed his belief that the current was stronger than usual with the master, neither the master nor the OOW independently monitored (except for the vessel's heading) the vessel's movement bodily across the channel. Neither the master nor the OOW challenged either the pilot's belief that the current was unusually strong or his course of action. While the port course alteration was being executed , the amount of the vessel's lateral motion (sideways crabbing) across the channel was not detected until it was too late and it was at this time that the pilot again asked for more RPM. At the time the vessel's lower side shell plating (in way of the turn of the bilge on the port side) 'slammed' the edge of the channel, it would appear that the RPM had returned to approximately 110 - because the pilot cancelled his request for an increase in RPM. The pattern of the damage sustained by the VULCAN is consistent with that which would be caused by the vessel striking an obstruction at the edge of the channel while the vessel was moving ahead and bodily sideways (crabbing). Because the two sounding surveys and bottom profile tests of the area between lights 'D69' and 'D71' revealed no anomalous depth or obstruction in the channel, the damage sustained by the VULCAN is also consistent with the vessel having struck an underwater obstruction outside the navigable portion of the channel. Although there was some exchange of information, the principles of Bridge Resource Management (BRM) which emphasize the importance of communication and of establishing an environment where all persons on the bridge feel free to question assumptions and intended actions were not in force. This situation allowed for a brief period when the cause of the vessel's loss of speed was not readily apparent to the pilot and the OOW. The result of this was that the allowance made for the set anticipated above light D 71 was greater than necessary. When the set experienced was less than anticipated, the vessel 'crabbed' rapidly across the channel, striking the obstruction outside the western limit of the channel.Analysis While proceeding up the deeper portion of the Amherstburg Channel, the forward speed of the VULCAN was observed to have decreased. The reduction in speed was due to a fall in the number of RPM of the main engine. Because the engine-room staff had not informed the bridge that a change-over from heavy to diesel fuel was taking place, which change-over normally requires a reduction in RPM, those on the bridge were not immediately aware of the cause of the loss of speed. The GPS speed reading of 5.5 to 5.6 knots was briefly taken as an indication by the pilot that the current in the area was abnormally strong. Because he suspected that the current was abnormally strong, the pilot intended to direct the vessel towards the western side of the channel to make allowance for the set he anticipated would set the vessel bodily to starboard after passing light 'D71'. Although the pilot discussed his belief that the current was stronger than usual with the master, neither the master nor the OOW independently monitored (except for the vessel's heading) the vessel's movement bodily across the channel. Neither the master nor the OOW challenged either the pilot's belief that the current was unusually strong or his course of action. While the port course alteration was being executed , the amount of the vessel's lateral motion (sideways crabbing) across the channel was not detected until it was too late and it was at this time that the pilot again asked for more RPM. At the time the vessel's lower side shell plating (in way of the turn of the bilge on the port side) 'slammed' the edge of the channel, it would appear that the RPM had returned to approximately 110 - because the pilot cancelled his request for an increase in RPM. The pattern of the damage sustained by the VULCAN is consistent with that which would be caused by the vessel striking an obstruction at the edge of the channel while the vessel was moving ahead and bodily sideways (crabbing). Because the two sounding surveys and bottom profile tests of the area between lights 'D69' and 'D71' revealed no anomalous depth or obstruction in the channel, the damage sustained by the VULCAN is also consistent with the vessel having struck an underwater obstruction outside the navigable portion of the channel. Although there was some exchange of information, the principles of Bridge Resource Management (BRM) which emphasize the importance of communication and of establishing an environment where all persons on the bridge feel free to question assumptions and intended actions were not in force. This situation allowed for a brief period when the cause of the vessel's loss of speed was not readily apparent to the pilot and the OOW. The result of this was that the allowance made for the set anticipated above light D 71 was greater than necessary. When the set experienced was less than anticipated, the vessel 'crabbed' rapidly across the channel, striking the obstruction outside the western limit of the channel. The bridge team was unaware that the engine-room staff were carrying out a change-over from heavy to diesel fuel. The change-over requires a reduction in engine RPM. The fuel change-over was not made in open water with room to manoeuvre but in a narrow constricted channel subject to cross-currents. The pilot briefly attributed the reduction in the vessel's speed to a stronger than normal current and made an allowance for set to stop the vessel being set bodily to starboard above light D 71. Neither the master nor the OOW challenged either the pilot's belief that the current was unusually strong or his course of action. The pattern of the damage sustained by the VULCAN is consistent with that which would be caused by the vessel striking an obstruction at the edge of the channel while the vessel was moving ahead and bodily sideways (crabbing). The damage sustained by the VULCAN is also consistent with the vessel having struck an underwater obstruction outside the navigable portion of the channel. Two post-occurrence sounding surveys and bottom profile tests of the area between lights 'D69' and 'D71' revealed no anomalous depth or obstruction in the channel nor, outside of the channel to within 12 to 24m of the shore. A post-occurrence verification of the main propulsion machinery confirmed that the machinery functioned as designed. There was no report of an abnormally strong current in the area of the occurrence. Both before and after the occurrence, vessels at a deeper draught than the VULCAN, navigated the area without incident. None of these vessels reported unusually strong currents. The vessel was not being navigated in a Bridge Resource Management environment; there was a lack of communication especially between the bridge and engine-room staff.Findings The bridge team was unaware that the engine-room staff were carrying out a change-over from heavy to diesel fuel. The change-over requires a reduction in engine RPM. The fuel change-over was not made in open water with room to manoeuvre but in a narrow constricted channel subject to cross-currents. The pilot briefly attributed the reduction in the vessel's speed to a stronger than normal current and made an allowance for set to stop the vessel being set bodily to starboard above light D 71. Neither the master nor the OOW challenged either the pilot's belief that the current was unusually strong or his course of action. The pattern of the damage sustained by the VULCAN is consistent with that which would be caused by the vessel striking an obstruction at the edge of the channel while the vessel was moving ahead and bodily sideways (crabbing). The damage sustained by the VULCAN is also consistent with the vessel having struck an underwater obstruction outside the navigable portion of the channel. Two post-occurrence sounding surveys and bottom profile tests of the area between lights 'D69' and 'D71' revealed no anomalous depth or obstruction in the channel nor, outside of the channel to within 12 to 24m of the shore. A post-occurrence verification of the main propulsion machinery confirmed that the machinery functioned as designed. There was no report of an abnormally strong current in the area of the occurrence. Both before and after the occurrence, vessels at a deeper draught than the VULCAN, navigated the area without incident. None of these vessels reported unusually strong currents. The vessel was not being navigated in a Bridge Resource Management environment; there was a lack of communication especially between the bridge and engine-room staff. The VULCAN struck an underwater obstruction outside the western limit of the Amherstburg Channel because officers on the bridge team were unaware that engine-room staff were making a fuel change-over which necessitated a reduction in main-engine RPM. The corresponding reduction in the vessel's speed was briefly attributed to a stronger than normal current and an over-correction was made to stop the vessel setting towards the east. The vessel was not effectively monitored for set and she was set bodily outside the western limit of the navigable channel. Full use was not made of the vessel's navigation equipment or of shore-based aids to navigation. A Bridge Resource Management environment was not in place to optimize the use of the bridge personnel.Causes and Contributing Factors The VULCAN struck an underwater obstruction outside the western limit of the Amherstburg Channel because officers on the bridge team were unaware that engine-room staff were making a fuel change-over which necessitated a reduction in main-engine RPM. The corresponding reduction in the vessel's speed was briefly attributed to a stronger than normal current and an over-correction was made to stop the vessel setting towards the east. The vessel was not effectively monitored for set and she was set bodily outside the western limit of the navigable channel. Full use was not made of the vessel's navigation equipment or of shore-based aids to navigation. A Bridge Resource Management environment was not in place to optimize the use of the bridge personnel.